{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T12:46:55Z","timestamp":1785847615809,"version":"3.56.0"},"reference-count":51,"publisher":"BMJ","issue":"3","license":[{"start":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T00:00:00Z","timestamp":1785801600000},"content-version":"unspecified","delay-in-days":34,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010269","name":"Wellcome Trust","doi-asserted-by":"publisher","award":["208378\/Z\/17\/Z"],"award-info":[{"award-number":["208378\/Z\/17\/Z"]}],"id":[{"id":"10.13039\/100010269","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["bmjph"],"accepted":{"date-parts":[[2026,4,30]]},"published-print":{"date-parts":[[2026,7]]},"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Individual participant data meta-analysis (IPD-MA) is the gold-standard approach for evidence synthesis. Poverty-related infectious diseases, a context in which standalone trials often have small sample sizes and consequently observe relatively few treatment failures, can benefit from this approach.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In collaboration with the global research community, the Infectious Diseases Data Observatory (IDDO) has developed a data platform for visceral leishmaniasis (VL)\u2014a neglected tropical disease (NTD), primarily to facilitate IPD-MA aimed at addressing questions of public health importance. Initially, a systematic review (SR) was undertaken to identify relevant trials since 1980 and study authors were invited to collaboratively develop the platform and participate in two IPD-MAs. IPD non-retrievability (data loss) was tracked and defined as unsuccessful attempts to contact study authors, or when the authors explicitly stated data loss, or declined participation.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The SR identified 147 VL trials (1983\u20132019), of which IPD was shared to the IDDO platform from 31 (21.1%). Reasons for data non-retrievability of 116 studies included: authors\u2019 retirement (n=42, 36.2%), data were lost (n=30, 25.9%), authors\u2019 non-response (n=22, 19.0%), authors were no longer contactable (n=17, 14.7%) and a lack of clarity over data ownership (n=5, 4.3%). The median sample size was 226 (IQR: 120\u2013542, range: 30\u20131,143) for retrieved studies compared with 81 (IQR: 34\u2013151, range: 7\u20133,126) for non-retrieved studies. No IPD were retrieved from trials published pre-2000 (0%, 0\/63). Following solicitation, the median time to complete data harmonisation was 633 days (n=29 studies).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Data solicitation and harmonisation steps remain underappreciated challenges in undertaking IPD-MA, particularly for NTDs where resources are severely limited. A critical mass of IPD from historical VL trials is no longer retrievable. It is imperative that further loss of such valuable data from ongoing and future trials is prevented.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjph-2025-003986","type":"journal-article","created":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T11:55:12Z","timestamp":1785844512000},"page":"e003986","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Data retrieval and harmonisation for individual participant data meta-analysis in the context of a neglected tropical disease: challenges and lessons from the Infectious Diseases Data Observatory visceral leishmaniasis data platform"],"prefix":"10.1136","volume":"4","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2158-846X","authenticated-orcid":false,"given":"Prabin","family":"Dahal","sequence":"first","affiliation":[{"name":"Infectious Diseases Data Observatory (IDDO), Oxford, UK"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sauman Singh","family":"Phulgenda","sequence":"additional","affiliation":[{"name":"Infectious Diseases Data Observatory (IDDO), Oxford, UK"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK"},{"name":"Coalition for Equitable Research in Low-Resource Settings (CERCLE), Paris, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gemma","family":"Buck","sequence":"additional","affiliation":[{"name":"Infectious Diseases Data Observatory (IDDO), Oxford, UK"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kasia","family":"Stepniewska","sequence":"additional","affiliation":[{"name":"Infectious Diseases Data Observatory (IDDO), Oxford, UK"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philippe J","family":"Guerin","sequence":"additional","affiliation":[{"name":"Infectious Diseases Data Observatory (IDDO), Oxford, UK"},{"name":"Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,8,4]]},"reference":[{"key":"2026080404550628000_4.3.e003986.1","doi-asserted-by":"crossref","DOI":"10.1136\/bmj.c221","article-title":"Meta-analysis of individual participant data: rationale, conduct, and reporting","volume":"340","author":"Riley","year":"2010","journal-title":"BMJ"},{"key":"2026080404550628000_4.3.e003986.2","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/j.jclinepi.2021.05.006","article-title":"PRIME-IPD SERIES Part 2. 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